邻苯二酚紫体系催化动力学光度法测定痕量锡(Ⅱ)

Catalytic kinetic spectrophotometric determination of trace Sn(Ⅱ) based on pyrocatechol violet system

基于痕量锡在0．5mol／L的H2SO4介质中对溴酸钾氧化邻苯二酚紫的褪色反应具有催化作用，建立了一种新的测定痕量锡的催化动力学光度法。确定了该褪色反应的最佳条件：0．5mol／LH2SO41．5mL；0．1mol／LKB如1．3mL；2．0×10^-4mol／L邻苯二酚紫3．5mL；反应时间为7min；反应温度为100℃。方法的检出限为4．51×10^-3μg/mL，线性范围为0-3μg／25mL。对该方法进行了精密度测定，其相对标准偏差为1．9％。研究了反应的动力学参数，确定了催化反应的的速率方程和表观活化能（En=34．10kJ／m01）。该方法可用于水样、人发中痕量锡的测定，相对标准偏差分别为0．32％和1．2％，标准加入回收率分别为99．2％和99．1％。

Based on the catalytic effect of tarce tin on discoloring reaction of pyrocatechol violet oxidized by potassium bromate in 0.5 mol/L sulphuric-acid solution, a new method for the determination of trace tin by catalytic kinetic spec- trophotometry was developed. The optimum reaction conditions were obtained as follows： 1.5 mL of 0.5 mol/L surfuric acid; 1.3 mL of 0.1 mol/L potassium bmmate; 3.5 mL of 2.0 ×10^-4 mol/L pyrocatechol violet; the reaction time is 7 min; the reaction temperature is 100℃. The detection limit is 4.51×10^-3 μg/mL and the linear range is 0-3 μg/25 mL for Sn^2＋. The precision of this method was tested and the relative standard deviation was 1.9%. The kinet- ic parameters of the discoloring reaction were investigated and the velocity equation and the apparent activation energy （Ea = 34.10 kJ/mol） were obtained. The method had high sensitivity and selectivity. The method was applied to the determination of trace tin in tap water and human hair samples with satisfactory results, and the relative standard deviations were 0.32% and 1.2% respectively, and the recoveries were 99.2% and 99.1%, respectively.